I skipped morning tourism because despite being deliberately abstemious at the wedding, I woke up with a seriously unhappy stomach. So I slept for a while and then went on a quest for just plain bread--I think if I'd been in a French-speaking country I could've bought a loaf at any store with counter service, but instead the two deli-ish places I tried had pastries and sandwiches and big hunks of cured meats, but no big hunks of bread. I had to go into an actual grocery store for a loaf of bread (and it wasn't very tasty, though I may have grabbed the wrong kind). But I also found some crackers that were exactly like miniature dry toast, which sounds terrible but was just what I wanted. Also, to my surprise, antacids are behind-the-counter items in Italian pharmacies. (Having no data on my phone, I had thought to look up the word back on the hotel's wifi. It is, fortunately, "antiacido.")
I met up with our group for a tour of the Basilica of San Clemente, which was great, and the Colosseum. San Clemente is a three-fer: a Middle Ages church with a ceiling and walls that were later redecorated but original mosaics up front, which are very beautiful and of which I have no pictures because they aren't allowed; try Wikimedia and this representative picture of the glorious floor; a fourth-century church underneath that, with frescos dating somewhat later; and two first-century buildings, one a Mithraeum and the other something probably commercial, like a warehouse. You have to pay to go into the excavations, and I'm not sure how informative the signs would be without a guide, but the top level is definitely worth a look.
Then to the Colosseum, which is of course giant and impressive: capacity of 40-70 thousand people! Designed to let them all out in ten minutes! Elevators to get the animals, special effects, gladiators, etc., up from down below the stage! A retractable roof! The exterior has just been cleaned and the interior is in progress, which makes an impressive difference, as you'll see in the pictures. We'd heard about the history on the first day's tour, plus it was very very hot, so it wasn't the absolutely fascinating experience it could've been on first meeting, but it was still really interesting.
Then dinner on the roof of the Hotel Artemide, which had amazing gelato--I don't know if they make it in-house, but I had cream, strawberry, mixed berry, and chocolate, and while the mixed berry was maybe a little too berry for my own tastes, it was all good, and the chocolate was a standout: stunningly intense.
The photo set is only for the Colosseum and includes one picture of the exterior from earlier in the trip.